Merge branch 'ps/history' into seen

* ps/history:
  builtin/history: implement "split" subcommand
  cache-tree: allow writing in-memory index as tree
  add-patch: add support for in-memory index patching
  add-patch: remove dependency on "add-interactive" subsystem
  add-patch: split out `struct interactive_options`
  add-patch: split out header from "add-interactive.h"
  builtin/history: implement "reword" subcommand
  builtin: add new "history" command
  replay: parse commits before dereferencing them
  replay: stop using `the_repository`
  replay: extract logic to pick commits
  wt-status: provide function to expose status for trees

Author: gitster

.gitignore

@@ -79,6 +79,7 @@
 /git-grep
 /git-hash-object
 /git-help
+/git-history
 /git-hook
 /git-http-backend
 /git-http-fetch

Documentation/git-history.adoc

@@ -0,0 +1,114 @@
+git-history(1)
+==============
+
+NAME
+----
+git-history - EXPERIMENTAL: Rewrite history of the current branch
+
+SYNOPSIS
+--------
+[synopsis]
+git history [<options>]
+git history reword [<options>] <commit>
+git history split [<options>] <commit> [--] [<pathspec>...]
+
+DESCRIPTION
+-----------
+
+Rewrite history by rearranging or modifying specific commits in the
+history.
+
+This command is similar to linkgit:git-rebase[1] and uses the same
+underlying machinery. You should use rebases if you either want to
+reapply a range of commits onto a different base, or interactive rebases
+if you want to edit a range of commits.
+
+Note that this command does not (yet) work with histories that contain
+merges. You should use linkgit:git-rebase[1] with the `--rebase-merges`
+flag instead.
+
+THIS COMMAND IS EXPERIMENTAL. THE BEHAVIOR MAY CHANGE.
+
+COMMANDS
+--------
+
+This command requires a subcommand. Several subcommands are available to
+rewrite history in different ways:
+
+`reword <commit> [--message=<message>]`::
+	Rewrite the commit message of the specified commit. All the other
+	details of this commit remain unchanged. If no commit message is
+	provided, then this command will spawn an editor with the current
+	message of that commit.
+
+`split [--message=<message>] <commit> [--] [<pathspec>...]`::
+	Interactively split up <commit> into two commits by choosing
+	hunks introduced by it that will be moved into the new split-out
+	commit. These hunks will then be written into a new commit that
+	becomes the parent of the previous commit. The original commit
+	stays intact, except that its parent will be the newly split-out
+	commit.
++
+The commit message of the new commit will be asked for by launching the
+configured editor, unless it has been specified with the `-m` option.
+Authorship of the commit will be the same as for the original commit.
++
+If passed, _<pathspec>_ can be used to limit which changes shall be split out
+of the original commit. Files not matching any of the pathspecs will remain
+part of the original commit. For more details, see the 'pathspec' entry in
+linkgit:gitglossary[7].
++
+It is invalid to select either all or no hunks, as that would lead to
+one of the commits becoming empty.
+
+CONFIGURATION
+-------------
+
+include::includes/cmd-config-section-all.adoc[]
+
+include::config/sequencer.adoc[]
+
+EXAMPLES
+--------
+
+Split a commit
+~~~~~~~~~~~~~~
+
+----------
+$ git log --stat --oneline
+3f81232 (HEAD -> main) original
+ bar | 1 +
+ foo | 1 +
+ 2 files changed, 2 insertions(+)
+
+$ git history split HEAD --message="split-out commit"
+diff --git a/bar b/bar
+new file mode 100644
+index 0000000..5716ca5
+--- /dev/null
++++ b/bar
+@@ -0,0 +1 @@
++bar
+(1/1) Stage addition [y,n,q,a,d,e,p,?]? y
+
+diff --git a/foo b/foo
+new file mode 100644
+index 0000000..257cc56
+--- /dev/null
++++ b/foo
+@@ -0,0 +1 @@
++foo
+(1/1) Stage addition [y,n,q,a,d,e,p,?]? n
+
+$ git log --stat --oneline
+7cebe64 (HEAD -> main) original
+ foo | 1 +
+ 1 file changed, 1 insertion(+)
+d1582f3 split-out commit
+ bar | 1 +
+ 1 file changed, 1 insertion(+)
+----------
+
+GIT
+---
+Part of the linkgit:git[1] suite

Documentation/meson.build

@@ -64,6 +64,7 @@ manpages = {
   'git-gui.adoc' : 1,
   'git-hash-object.adoc' : 1,
   'git-help.adoc' : 1,
+  'git-history.adoc' : 1,
   'git-hook.adoc' : 1,
   'git-http-backend.adoc' : 1,
   'git-http-fetch.adoc' : 1,

Makefile

@@ -1274,6 +1274,7 @@ LIB_OBJS += repack-geometry.o
 LIB_OBJS += repack-midx.o
 LIB_OBJS += repack-promisor.o
 LIB_OBJS += replace-object.o
+LIB_OBJS += replay.o
 LIB_OBJS += repo-settings.o
 LIB_OBJS += repository.o
 LIB_OBJS += rerere.o
@@ -1407,6 +1408,7 @@ BUILTIN_OBJS += builtin/get-tar-commit-id.o
 BUILTIN_OBJS += builtin/grep.o
 BUILTIN_OBJS += builtin/hash-object.o
 BUILTIN_OBJS += builtin/help.o
+BUILTIN_OBJS += builtin/history.o
 BUILTIN_OBJS += builtin/hook.o
 BUILTIN_OBJS += builtin/index-pack.o
 BUILTIN_OBJS += builtin/init-db.o